[PATCH bpf 4/5] bpf: fix map permissions check

[Anton Protopopov]

The map_lookup_and_delete_elem() function should check for both FMODE_CAN_WRITE
and FMODE_CAN_READ permissions because it returns a map element to user space.

Fixes: bd513cd08f10 ("bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall")

Signed-off-by: Anton Protopopov <a.s.protopo...@gmail.com>
---
 kernel/bpf/syscall.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e6dee19a668..5e52765161f9 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1468,7 +1468,8 @@ static int map_lookup_and_delete_elem(union bpf_attr 
*attr)
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);
-       if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
+       if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ) ||
+           !(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
                err = -EPERM;
                goto err_put;
        }
-- 
2.20.1